1. Field of the Invention
The present invention relates to a signal detection system of a touch screen, and more particularly to a signal detection system of a large-sized mutual capacitive multi touch screen that is capable of effectively reducing RC time delay, signal distortion, an effect of noise, parasitic resistance, and parasitic capacitance.
2. Description of the Related Art
With widespread popularization in recent years, touch screens have been used in various devices, such as an automatic teller machine (ATM), a kiosk, a point of sale (POS) system, a personal digital assistant (PDA), a navigator, an MP3 player, a smart phone, and a tablet PC. The touch screens are in the spotlight in terms of providing a convenient interface. It is expected that the demand for the touch screen will continue to increase in various fields with the development of the information technology (IT) industry.
Currently commercialized touch screens generally include a resistive touch screen, a surface acoustic wave (SAW) touch screen, an infrared touch screen, an optical or camera type touch screen, and a capacitive touch screen, all of which have advantages and disadvantages.
Among the above-mentioned touch screens, the capacitive touch screen is superior to the other type touch screens in that it is possible to realize an accurate multi touch function and thus has highest percentage of the market. The capacitive touch screen is adopted in most smart phones and tablet PCs, which have been popularized in recent years.
In the capacitive touch screen, when voltage is applied to a panel and an object, such as a finger, touches the panel, the touch point is recognized based on variation of voltage due to capacitance generated between the finger and the panel. Also, the capacitive touch screen has advantages in that the capacitive touch screen exhibits higher resolution, durability, and transmittance than the other type touch screens, the capacitive touch screen is manufactured with low cost except for the resistive touch screen, and it is possible to recognize multiple touches without difficulty while being little affected by surface foreign matter or the surroundings like the infrared touch screen, the surface acoustic wave touch screen, and the optical or camera type touch screen.
As described above, the capacitive touch screen is superior to the other type touch screens in terms of several characteristics. In case of realizing a large-sized multi touch screen, however, parasitic resistance and capacitance present in a touch panel are increased with the increase in size of the touch panel with the result that RC time delay is excessively increased. For this reason, it is difficult to manufacture such a large-sized multi touch screen.
With promotion of smart education based on IT technology by Ministry of Education & Science Technology in Korea in recent years, the demand for a large-sized multi touch screen has been increased. Due to technical limitations of a capacitive touch screen, however, most large-sized multi touch screens have been manufactured as an infrared touch screen or a camera type touch screen.
In the infrared touch screen or camera type touch screen, when the number of touch points is increased, an additional algorithm is necessary to recognize the touch points. For this reason, the infrared touch screen or camera type touch screen is not considered to realize true multiple touches. In addition, the infrared touch screen or camera type touch screen has lower efficiency and accuracy than the capacitive touch screen.
Accordingly, much research and development have been conducted into a large-sized capacitive touch screen capable of correctly recognizing multiple touches and exhibiting excellent touch characteristics.